9-132897596-C-T

Variant names:

• chr9-132897596-C-T
• rs1218889799
• NM_000368.5:c.2640G>A

Variant summary

Our verdict is Uncertain significance. Variant got 0 ACMG points: 2P and 2B. PM2 BP4_Moderate

The NM_000368.5(TSC1):​c.2640G>A​(p.Met880Ile) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000297 in 1,009,734 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 12/21 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another nucleotide change resulting in the same amino acid substitution has been previously reported as Uncertain significance in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. M880T) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 29)
  • Exomes 𝑓: 0.0000030 (0 hom.)
• Consequence: TSC1 NM_000368.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:3
• Conservation: PhyloP100: 2.29

Genes affected

TSC1 (HGNC:12362): (TSC complex subunit 1) This gene is a tumor suppressor gene that encodes the growth inhibitory protein hamartin. The encoded protein interacts with and stabilizes the GTPase activating protein tuberin. This hamartin-tuberin complex negatively regulates mammalian target of rapamycin complex 1 (mTORC1) signaling which is a major regulator of anabolic cell growth. This protein also functions as a co-chaperone for Hsp90 that inhibits its ATPase activity. This protein functions as a facilitator of Hsp90-mediated folding of kinase and non-kinase clients, including TSC2 and thereby preventing their ubiquitination and proteasomal degradation. Mutations in this gene have been associated with tuberous sclerosis and lymphangioleiomyomatosis. [provided by RefSeq, May 2022]

ACMG classification

Verdict is Uncertain_significance. Variant got 0 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• BP4: Computational evidence support a benign effect (MetaRNN=0.21429613).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TSC1	NM_000368.5	c.2640G>A	p.Met880Ile	missense_variant	Exon 21 of 23	ENST00000298552.9	NP_000359.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TSC1	ENST00000298552.9	c.2640G>A	p.Met880Ile	missense_variant	Exon 21 of 23	1	NM_000368.5	ENSP00000298552.3
TSC1	ENST00000490179.4	c.2640G>A	p.Met880Ile	missense_variant	Exon 22 of 24	3		ENSP00000495533.2

Frequencies

GnomAD3 genomes Cov.: 29

GnomAD4 exome AF: 0.00000297 AC: 3 AN: 1009734 Hom.: 0 Cov.: 37 AF XY: 0.00000195 AC XY: 1 AN XY: 511876

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000400

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 29

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:3

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not provided Uncertain:1

Apr 11, 2022

GeneDx

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant does not alter protein structure/function; Has not been previously published as pathogenic or benign to our knowledge; This variant is associated with the following publications: (PMID: 18466115) -

Tuberous sclerosis 1 Uncertain:1

Apr 25, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces methionine, which is neutral and non-polar, with isoleucine, which is neutral and non-polar, at codon 880 of the TSC1 protein (p.Met880Ile). This variant is not present in population databases (gnomAD no frequency). This variant has not been reported in the literature in individuals affected with TSC1-related conditions. ClinVar contains an entry for this variant (Variation ID: 852506). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is not expected to disrupt TSC1 protein function with a negative predictive value of 95%. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Hereditary cancer-predisposing syndrome Uncertain:1

Jun 26, 2024

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.M880I variant (also known as c.2640G>A), located in coding exon 19 of the TSC1 gene, results from a G to A substitution at nucleotide position 2640. The methionine at codon 880 is replaced by isoleucine, an amino acid with highly similar properties. This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Based on the available evidence, the clinical significance of this variant remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.59
BayesDel_addAF	Benign	-0.0092	T
BayesDel_noAF	Benign	-0.25
CADD	Benign	22
DANN	Uncertain	0.99
DEOGEN2	Benign	0.32	T;.;T;.;.;T;.;T;.;.;.
Eigen	Benign	0.019
Eigen_PC	Benign	0.20
FATHMM_MKL	Pathogenic	0.98	D
LIST_S2	Benign	0.84	.;T;T;T;T;.;.;.;T;T;.
M_CAP	Benign	0.072	D
MetaRNN	Benign	0.21	T;T;T;T;T;T;T;T;T;T;T
MetaSVM	Benign	-0.50	T
MutationAssessor	Benign	0.76	N;.;N;.;.;N;.;N;.;.;.
PrimateAI	Uncertain	0.57	T
PROVEAN	Benign	-0.13	N;N;N;.;.;.;.;.;.;.;.
REVEL	Uncertain	0.30
Sift	Benign	0.25	T;T;T;.;.;.;.;.;.;.;.
Sift4G	Benign	0.13	T;T;T;.;.;.;.;.;.;.;.
Polyphen		0.083	B;.;B;.;.;B;.;B;.;.;.
Vest4		0.47
MutPred		0.26		Loss of disorder (P = 0.05);.;Loss of disorder (P = 0.05);.;.;Loss of disorder (P = 0.05);.;Loss of disorder (P = 0.05);.;.;.;
MVP		0.30
MPC		0.56
ClinPred		0.66	D
GERP RS		5.8
Varity_R		0.31
gMVP		0.21

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1218889799; hg19: chr9-135772983; COSMIC: COSV53763744; COSMIC: COSV53763744;